As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Friday 5 October 2018

How birds can stay slim, even when they overeat



Date:  September 18, 2018
Source:  Cell Press

Noticing that songbirds, such as finches, never seem to get fat despite overeating at bird feeders, London environmental biologist Lewis Halsey wondered whether the amount of energy birds put into singing, fidgeting, or exercising could be adjusted in ways that regulate weight. In a literature review published September 18 in the journal Trends in Ecology & Evolution, he explores whether songbirds don't need to worry about their calorie counts because they can control the way their bodies use energy.

"The passerine birds at the bird feeders near my home never seem to get fat despite having this buffet constantly available to them, but there are people who get heavy when exposed to that kind of all-you-can-eat environment," says Halsey of the University of Roehampton. "I wanted to investigate possible behavioral and physiological mechanisms, aside from just food consumed and exercise completed, that help animals control their energy budgets and body weights; there's more going on than just how many calories you've put into your face."

Now, it could be that we never see fat songbirds because the ones that gain too much weight are picked off by a range of predators. However, that predation pressure would eventually cause evolution to weed out such a tendency, and recent studies indirectly suggest that birds are capable of balancing energy intake by increasing their daily metabolic rate or decreasing the efficiency with which they are able to extract energy from ingested food.

"For a given amount of food, an animal can unconsciously adjust how efficiently it uses the energy from it either behaviorally, for example by changing wingbeat frequency or singing patterns to use more or less energy, or physiologically, in terms of digestive or cellular metabolic efficiency," Halsey says.

No comments:

Post a Comment